1. Field of The Invention
The present invention relates to thickened cleaning compositions having a viscoelastic rheology, and in particular to such viscoelastic cleaning compositions and methods of use having improved phase and rheological stability.
2. Description of Related Art
Much art has addressed the problem of developing a thickened cleaning composition, which may contain a bleach and may have utility as a hard surface cleanser. The efficacy of such compositions is greatly improved by viscous formulations, increasing the residence time of the cleaner. Splashing during application and use is minimized, and consumer preference for a thick product is well documented. Schilp, U.S. Pat. No. 4,337,163 shows a hypochlorite thickened with an amine oxide or a quaternary ammonium compound, and a saturated fatty acid soap. Stoddart, U.S. Pat. No. 4,576,728 shows a thickened hypochlorite including 3- or 4-chlorobenzoic acid, 4-bromobenzoic acid, 4-toluic acid and 3-nitrobenzoic acid in combination with an amine oxide. DeSimone, U.S. Pat. No. 4,113,645 discloses a method for dispersing a perfume in hypochlorite using a quaternary ammonium compound. Bentham, et al., U.S. Pat. No. 4,399,050, discloses hypochlorite thickened with certain carboxylated surfactants, amine oxides and quaternary ammonium compounds. Jeffrey, et al., GB 1466560 shows bleach with a soap, surfactants and a quaternary ammonium compound. For various reasons, the prior an thickened hypochlorite compositions are not commercially viable. In many instances, thickening is insufficient to provide the desired residence time on non-horizontal surfaces. Adding components, and/or modifying characteristics of dissolved components often creates additional problems with the composition, such as syneresis, which require adding further components in an attempt to correct these problems. Polymer thickened hypochlorite bleaching compositions tend to be oxidized by the hypochlorite. Prior art thickened bleach products generally exhibit phase instability at elevated (above about 100.degree. F.) and/or low (below about 35.degree. F.) storage temperatures. Difficulties exist with colloidal thickening agents in that these tend to exhibit either false-bodied or thixotropic rheologies, which, at high viscosities, can result in a tendency to set up or harden. Other hypochlorite compositions of the prior art are thickened with surfactants and may exhibit hypochlorite stability problems. Surfactant thickening systems also are not cost effective when used at the levels necessary to obtain desired product viscosity values. European Patent Application 0,204,479 to Stoddard describes shear-thinning compositions, and seeks to avoid viscoelasticity in such shear-thinning compositions.
Drain cleaners of the art have been formulated with a variety of actives in an effort to remove the variety of materials which can cause clogging or restriction of drains. Such actives may include acids, bases, enzymes, solvents, reducing agents, oxidants and thioorganic compounds. Such compositions are exemplified by U.S. Pat. Nos. 4,080,305 issued to Holdt, et al.; 4,395,344 to Maddox; 4,587,032 to Rogers; 4,540,506 issued to Jacobson, et al;. 4,610,800 to Durham, et al.; and European Patent Applications 0,178,931 and 0,185,528, both to Swann, et al. Generally, workers in this field have directed their efforts toward actives, or combinations of actives, which would have improved efficacy or speed when used on typically-encountered clog materials; or are safer to use. A problem with this approach, however, is that regardless of the effectiveness of the active, if the composition is not fully delivered to the clog, the effectiveness of the active will be diminished or destroyed. This is particularly apparent where the clogged drain results in a pool of standing water, and a drain opener composition added to such standing water will be substantially diluted thereby. The above European Patent Applications of Swann, et al. disclose an attempt to overcome the delivery problem by encapsulating actives in polymeric beads. The Rogers and Durham, et al. patents refer to the delivery problem and mention that a thickener is employed to increase the solution viscosity and mitigate dilution. Similarly, a thickener is optionally included in the formulation of Jacobson, et al.
The parent application disclosed such cleaning compositions with quaternary ammonium surfactants, preferably CETAC as discussed below, and either a single counterion or mixed counterions for providing enhanced rheological properties while maintaining phase stability of the composition.